Thursday 22 February 2018

Snake-hunting birds stamp on prey with force five times their weight, says study

A secretary bird named Madeleine attacking his prey. (JASON SHALLCROSS)
A secretary bird named Madeleine attacking his prey. (JASON SHALLCROSS)

Snake-hunting secretary birds stamp on and kill their prey with a force equivalent to five times their body weight, a study has shown.

A team of British scientists made the discovery after conducting tests on a captive secretary bird called Madeleine.

The researchers trained Madeleine - who is a he, not a she - to attack a rubber snake, and measured the strength of his kicks with a force plate concealed beneath the "prey".

The tests, conducted at the Hawk Conservancy Trust in Hampshire, showed that Madeleine lashed out with a force of 195 Newtons, equivalent to five times his own body weight.

It took an average of just 15 milliseconds (ms) for his feet to make contact with the "snake".

Lead researcher Dr Steve Portugal from the School of Biological Sciences at Royal Holloway, University of London, said: "The exceptionally rapid strike contact duration is a tenth of the time it takes to blink an eye - which takes around 150 ms.

"Such rapid time, coupled with the exceptionally long legs, means the birds can't be using proprioreception, the sixth sense we use to sense our position and movement.

"Therefore, they are using visual targeting and feed-forward motor control - pre-planned movements - during strike events."

Co-author Dr Monica Daley, from the Royal Veterinary College, explains: "There are interesting potential technological applications in 'biologically inspired' control of exceptionally fast movement in robots and prosthetics.

"A comparable task might be playing baseball with a prosthetic arm, which requires very fast, forceful and accurate arm movements for pitching and batting."

The findings are reported in the journal Current Biology.

Secretary birds live on open grasslands in Africa where they prey on a variety of small animals which are hunted on foot, including deadly poisonous snakes.

Press Association

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